The audit process should be the same no matter what firewall you are
dealing with. There are a couple of things you should be aware of in
regards to Cisco Pix firewalls as:

1. Security levels 100 trusted 0 non trusted, DMZ usually fall in
between these two numbers.

2. Network Address Translation. PAT (port address translation many to
one or to a pool address), Static one to one.

3. ACL's to individual interfaces which are applied in the inbound
direction only. Packets are allowed from a higher security level
interface toward a lower one without the need of an acl. For this to
occur NAT, PAT and/or Static must be configured first. In the case of
from lower to higher an acl is needed permitting this access.

I would highly recommend you to read the release version the Pix is
running beforehand to have a general understanding on how the pix
performs packet processing and filtering.